I'd play 3-5-2, with a midfield three of Barry, Cleverley and Davies (dropping Barkley, purely for tactical reasons).
Get Bolasie up close to Rom, and those two can definitely cause Cahill and Luiz serious problems, if our transition play and our out ball is good enough. A lot of the time it will effectively be a 5-3-2, because you'd expect Chelsea to monopolise possession, but that's fine. We kept City at arms length (aside from Jags' aberrations) and they are a better attacking force than Chelsea.
Chelsea have been stronger in recent times, but they still have vulnerabilities, players not playing in their natural positions (Moses and Azpilicueta), shit players (Cahill), and people who can go completely missing if you can get on top of them early on (Hazard).
I think we can win this.